title: Beta 1 integrin-mediated collagen gel contraction is stimulated by PDGF.
abstract: The attachment of primary rat hepatocytes and fibroblasts to collagen type I is mediated by non-RGD-dependent beta 1 integrin matrix receptors. In this report we describe a novel 96-well microtiter plate assay for the quantification of fibroblast-mediated contraction of floating collagen type I gels. Fetal calf serum and platelet-derived growth factor (PDGF), but not transforming growth factor-beta 1, stimulated primary rat heart fibroblasts and normal human diploid fibroblasts (AG 1518) to contract collagen gels to less than 10% of the initial gel volume within a 24-h incubation period. Rabbit polyclonal antibodies directed to the rat hepatocyte integrin beta 1-chain inhibited the PDGF-stimulated collagen gel contraction. The inhibitory activity on contraction of the anti-beta 1 integrin IgG could be overcome by adding higher doses of PDGF. The contraction process was not blocked by anti-fibronectin IgG nor by synthetic peptides containing the tripeptide Arg-Gly-Asp (RGD), in concentrations that readily blocked fibroblast attachment to fibronectin-coated planar substrates. Autologous fibronectin or control peptides containing the tripeptide Arg-Gly-Glu were without effect. Immunofluorescence microscopy on fibroblasts grown within collagen gels revealed a punctate distribution of the beta 1 integrin and a lack of detectable levels of endogenously produced fibronectin. Collectively these data suggest a role for integrin collagen receptors with affinity for collagen fibers, distinct from the previously described RGD-dependent fibronectin receptors, in the fibronectin-independent PDGF-stimulated collagen gel contraction process.
authors.affiliation: Department of Medical and Physiological Chemistry, Biomedical Center, Uppsala, Sweden.
authors.forename: D
authors.initials: D
authors.lastname: Gullberg
authors.forename: A
authors.initials: A
authors.lastname: Tingström
authors.forename: A C
authors.initials: AC
authors.lastname: Thuresson
authors.forename: L
authors.initials: L
authors.lastname: Olsson
authors.forename: L
authors.initials: L
authors.lastname: Terracio
authors.forename: T K
authors.initials: TK
authors.lastname: Borg
authors.forename: K
authors.initials: K
authors.lastname: Rubin
mesh_terms: D000199:Actins / Q000032:analysis; D000595:Amino Acid Sequence; D000818:Animals; D001769:Blood; D002460:Cell Line; D003094:Collagen / Q000378:metabolism*; D005347:Fibroblasts / Q000032:analysis / Q000502:physiology*; D005353:Fibronectins / Q000276:immunology / Q000494:pharmacology; D005782:Gels; D006801:Humans; D007074:Immunoglobulin G / Q000494:pharmacology; D016023:Integrins / Q000032:analysis / Q000276:immunology / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D051381:Rats; D011994:Recombinant Proteins; D015291:Transforming Growth Factors / Q000494:pharmacology
chemical_list: D000199:Actins; D005353:Fibronectins; D005782:Gels; D007074:Immunoglobulin G; D016023:Integrins; D009842:Oligopeptides; D010982:Platelet-Derived Growth Factor; D011994:Recombinant Proteins; D015291:Transforming Growth Factors; D003094:Collagen